1. Field of the Invention
The present invention relates to positive type electrodeposition photoresist compositions, as well as to formation processes, using the compositions, for pattern useful to circuit formation of electronic devices, materials for printing etc.
2. Description of the Prior Art
Currently, positive type photoresists are widely used for formation of circuit patterns of electronic devices etc. As positive type aqueous resist compositions used for these applications, in many cases, resins, which dissolve or disperse in water by neutralization and chemically bound with a quinone diazide compound, are used in the form of aqueous solution or dispersion.
These compositions form a resist film by utilizing a reaction in which the quinone diazide group is photo-decomposed when irradiated with an ultraviolet light and forms an indenecarboxylic acid via a ketene.
The resist compositions using quinone diazide compound, however, are weakly photoreactive to a visible light and hence, there are problems of insufficient resolution etc. in case a formation of a very fine pattern is necessary. Moreover, the quinone diazide group is unstable in aqueous systems, and hence, there is a difficulty in using the composition containing a quinone diazide group in applications that require prolonged stability of the composition in a bath as in the electrodeposition coating process.
The present inventors previously proposed, as positive type electrodeposition photoresist compositions replacing these, a composition sensitive also to a visible light comprising a polymer having carboxyl group(s) and occasionally phenolic hydroxyl group(s), a compound having a plurarity of vinyl ether groups, and a compound which is decomposed and generates an acid when irradiated with an actinic ray (U.S. Pat. No. 5,527,656; Japanese Laid-open Patent Publications No. 313134/1994, 313135/1994, and 313136/1994. These compositions are photosensitive electrodeposition compositions which function according to a mechanism that the film formed from them becomes insoluble in solvents and aqueous alkaline solutions through crosslinking by an addition reaction between carboxyl group(s) and vinyl ether group(s) when heated, and when it is further irradiated with an actinic ray and then heated, the exposed portions become soluble in solvents and aqueous alkaline solutions again as the crosslinked structure is severed by the catalytic action of the acid generated by the irradiation.
These compositions have advantages such as having high transparency to actinic rays, because they need not contain a large amount of a functional group of high extinction coefficient unlike resists using quinone diazide as a photosensitizer and having high sensitivity as positive type photosensitive composition because the acid generated at the exposed portions acts as catalyst, when heated, to sever the crosslinked structure in the form of a chain reaction.
However, the heating time is required to be shortened in respect of productivity, when these photosensitive electrodeposition compositions are coated on a substrate and heated for crosslinking. When a shortening of the time is tried by heating at a higher temperature than 100.degree. C., there is the problem that the compound, which generates an acid when irradiated with an actinic ray, existing in said photosensitive electrodeposition composition, generates an acid already before being irradiated by a visible light and thus the whole formed film is dissolved when developed. Therefore, an improvement of the thermal stability of said photosensitive electrodeposition composition is strongly demanded in said technical field.